In manufacturing semiconductor devices, recently, the necessity of an etching process for thinning a semiconductor wafer with a pattern is increasing.
In such an etching process, a wet etching apparatus for etching a semiconductor wafer while supplying an etchant is used. In a conventional wet etching method, a dummy wafer is etched to confirm the etching rate in advance, and the etching end time is determined on the basis of the etching rate.
However, when such an etching time management method is used, an extra process for etching a dummy wafer is necessary in addition to an actual etching process. In addition, the etching rate may change for each etching process. For this reason, time management assuming a fixed etching rate generates a variation in thickness of resultant semiconductor wafers.
To increase the etching accuracy or operation efficiency in the etching process, the thickness of a semiconductor wafer portion must be measured in situ during etching. With this measurement, data of a change in thickness over time during etching can be obtained whereby the end time can be obtained for each etching process. That is, various etching processes can be managed and controlled.